1. Field of Invention
The present invention relates to a hydraulic pressure clutch. More particularly, the present invention relates to a hydraulic pressure clutch provided with more than two clutches and a plurality of oil passages.
2. Description of Related Art
An automatic transmission is an apparatus for shifting gears to a appropriate shift gear according to vehicle's running state. Generally an automatic transmission includes at least one planetary gear set including a sun gear, a ring gear, and a planet carrier as operating members, and friction elements such as a clutch and a brake for controlling operations of the operating members.
And also the automatic transmission further includes a hydraulic control system for controlling the friction members hydraulically. The clutches and brakes are controlled to be engaged or disengaged by operation of the hydraulic control system according to each shift gear so that each shift gear is realized.
The clutch of the friction members transmits power of an engine to the operating member of the planetary gear set or delivers power between the operating members. The clutch may be used for delivering power for various machines as well as for the automatic transmission.
The clutch includes a piston, a plurality of clutch plates and a plurality of friction disks alternately disposed with the plurality of clutch plates. When hydraulic pressure is supplied to the piston, the clutch plate moves to contact the friction disk and ultimately, the gear shift is shifted to a target gear shift. When the hydraulic pressure is released from the piston, the piston returns to an original position by a return spring and so on, and the clutch plate moves to be separated from the friction disk by a reaction plate and so on, and ultimately, the operation members are released.
A friction element of an automatic transmission is controlled by hydraulic pressure and thus a plurality of oil passages is required. And if scheme of the oil passage is complicated, a space for operating each a friction element has to be increased. And thus length of an automatic transmission is to be increased.
Recently an automatic transmission for a front-wheel-drive car has been developed to be multiple gear shifts, and thus total length increase of the automatic transmission may disturb to mount the automatic transmission into an engine room. And thus, if axial direction length for a clutch is reduced, length of an automatic transmission may be reduced. And also, an automatic transmission which may realize multiple gear shifts may be mounted into a front-wheel-drive car.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.